Roller for hot and cold rolling and method of making the same

ABSTRACT

A roller for hot and cold rolling is made by taking a hard metal ring, the cross-section of which decreases radially outwardly, and casting around the inside and at least the inner part of the radial sides thereof an annular hub of ferro alloy. After casting, the hub and the hard metal ring are cooled, the hub shrinking more than the hard metal ring so as to exert compressive forces thereagainst to hold the same in place.

United States Patent 1191 Loqvist 1 1 Jan. 29, 1974 [5 ROLLER FOR HOTAND COLD ROLLING 2,342,159 2/1944 Moran 5. 29/125 AND METHOD OF MAKINGTHE SAME 3,432,902 3/1969 Rackoff et a1. 29/125 3,435,499 4/1969 Rackoffet a1. 29/125 Inventor! j Ragnar q Fagersta. 3,577,619 5/1971 Strandel29/125 x Sweden 3,667,096 6/1972 Edsmar 29/125 [73] Ass gnee Fagerstalag Fagersta 3,609,849 10/1971 Krol 29/132 Sweden Primary ExaminerA1fredR. Guest [22] led: 1971 Attorney, Agent, or FirmLarson, Taylor & Hinds[21] Appl. No.: 210,440

[57] ABSTRACT [30] Foreign ApplicationvPriority Data l Jan 8 1971 SwedenIIIIIIIIIIIIIII 170/71 A roller for hot and cold rolling 1s made bytaking a hard metal ring, the cross-section of which decreases 52 us.c1. 29/125 radially outwardly and casting the inside and 511 1m. (:1B2lb 31/08 21.116981111611111 part rad'al sides themfa" [58] Field ofSearch M 29/132 130 129 5 125 nular hub of ferro alloy. After casting,the hub and the hard metal ring are cooled, the hub shrinking more [56]References Cited than thehard metal ring so as to e tert compressiveUNITED STATES PATENTS forces thereagainst to hold the same in place.

1,413,436 4/1922 Vedder 29/125 4 Claims, 4 Drawing Figures ROLLER FORHOT AND COLD ROLLING AND METHOD OF MAKING THE SAME The present inventionrefers to a roller for hot-rolling and/or cold-rolling, in which therolling surface is formed by a hard metal ring on a roller body or hubof a ferro alloy, for instance steel. In manufacturing rollers having arolling surface of hard metal it is for economical reasons desirablethat the amount of hard metal is as low as possible. Generally the hardmetal ring is connected to the roller body by a mechanical joint means.This necessitates small tolerances, which results in cost demandingmanufacturing operations as for instance grinding. Further, assembliesof this kind are sensitive to temperature variations, and the hard metalring has a tendency to burst.

The object of the invention is to eliminate the disadvantages of priorknown assemblies of this kind, and it is thereby characterized, that theroller body is cast around the hard metal ring, and that the crosssectional width of the hard metal ring increases from the rollingsurface towards the centre of the roller, so that a prestressing isobtained of the hard metal ring when located in the body or hub of aferro alloy, for instance steel.

Since the roller body or hub is cast around the hard metal ring it is nolonger necessary to grind same before the mounting operation as in priorknown hard metal roller assemblies. The hard metal ring is kept securedin the hub due to the compressive stresses which are exerted against theside edges of the hard metal ring by the hub. The compressive stressesderive from the difference in coefficients of expansion between the hardmetal and the ferro alloy or steel. The magnitude of the compressivestresses may be regulated for instance by varying the inclination of theside edges of the hard metal ring in relation to the shaft of theroller. The side edges may also be wave-formed or formed with grooves orother unevennesses in order to get a better transmission of the torquebetween the hard metal ring and the hub. The casting may be done in asand mould or cast iron mould or in any other known way.

An example of the cast around of a hard metal ring in a hub of a ferroalloy or steel in accordance with the invention will be described in thefollowing.

The cast iron mould is firstly treated with for instance an emulsion ofoil and graphite. The cast iron mould with the hard metal ring is putinto a furnace and is preheated to for instance 600 C for the preventionof blister formation in the casting and for the reduction of the effectsdue to the differences in the thermal expansivities. The heating shouldtake place in an atmosphere of protective gas or vacuum for preventingoxidizing of the hard metal ring and the cast iron mould. Then the ferroalloy lump is poured into the mould. The successive cooling should takeplace slowly in order that the ferro alloy shall not be brittle. After asuitable time the ferro alloy/hard metal piece is removed from the castiron mould and is packed into a heat isolating material. The hard metalpiece may also be packed into the heat isolating material without havingbeen removed from the cast iron mould.

In the accompanying drawings is shown a hard metal ring assembly,

FIG. 1 is a side-view of a hard metal ring,

FIG. 2 is a cross-section along the line II II of FIG. 1.

- v FIGJS is a side-view of a roller assembly according to'theinvention, and

FIG. 4 is a cross-section along the line IV IV of FIG. 3.

In the drawings the reference number 1 indicates a hard metal ringintended to have cast around it the roller body or hub 2 of a ferroalloy, for instance steel. The hard metal ring I is provided withgrooves 7 on the opposite side edges thereof. It is evident from FIGS. 2and 4,. that the side edges 6 of the hard metal ring 1 converge somewhatin the direction radially outwards. In FIGS. 3 and 4 the hard metal ringI is shown with the body or hub 2, cast around it and during the coolingthe ferro alloy or steel shrinks more than the hard metal, and thereforea cleft is formed under the hard metal ring 1 between same and the body2.

After the body or hub has cooled the assembly of the ferro alloy bodyand the hard metal piece are turned clean and holes 8 are bored in thebody for injecting for instance a re-inforced epoxi base thermosettingresin or any other suitable support material in the cleft 3 under thehard metal ring. During the cooling following the casting correcttemperature difference is kept between the hard metal and the ferroalloy lump (higher for the hard metal) by adding heat to the hard metalring while the centre of the casting is cooled for instance by means ofair.

Because of the axial and radial mounting of the hard metal ring 1 in thebody 2 water cooling, which is normally necessary, can be eliminated orreduced. By suitably providing cooling rings or cooling flanges on theside edges of the hub the temperature of the roller may be controlled.For the purpose of preventing temperature transportation from therolling surface of the hard metal ring 1 to the roller shaft the part ofthe hub 2 engaging the shaft may be provided with a heat protectionshell 4 of for instance titanium oxide or any other suitable heatinsulating material.

By utilizing a cast iron mould enabling a cooling of the centre of thehub during the casting the effect of the differences in thermalexpansivities can be controlled. The basic feature thereby is that thetemperature differences are kept between the ferro alloy and the hardmetal parts. The temperatures of the ferro alloy and the hard metalrespectively are chosen with respect to their thermal expansivity, i.e.,the ferro alloy or steel is kept at lower temperature than the hardmetal. This may be done for instance by adding heat to the outside ofthe cast iron mould by means of for instance high frequency currentswhile the centre thereof is cooled by means of for instance air orwater.

The advantages of the roller assembly according to the present inventioncompared with prior known rollers are above all that it is cheaper tomanufacture, essentially less sensitive to temperature increases, and ithas a longer duration due to the fact that water cooling of the rollingsurface may be eliminated or reduced,- which means that the temperaturegradients between the rolling material and the roller become lessstrong.

I claim:

1. A roller for hot and cold-rolling comprising: a hard metal ring, thecross-section of which decreases radially outwardly, a one-piece cast inannular ferro alloy hub, the radial inner surface and the inner part ofthe sides of the hard metal ring being positioned within the outercircumference of the hub with the latter stressed against the sides ofthe hard ring to hold it in place in the hub, wherein an annular cleftis formed between the hard metal ring and the ferro alloy hub adjacentthe inside of the hard metal ring.

2. A roller according to claim 1, in which the side sur- 3. A rolleraccording to claim 1, including a supporting material located in saidcleft.

4..A roller according to claim 1, including cooling faces of the ringhave radially extending grooves 5 flangesformed on the exterior of the tl t

2. A roller according to claim 1, in which the side surfaces of the ringhave radially extending grooves formed therein.
 3. A roller according toclaim 1, including a supporting material located in said cleft.
 4. Aroller according to claim 1, including cooling flanges formed on theexterior of the hub.